Graticule's DayPlanna software application solves the "travelling salesman" problem. Given a set of locations to visit, DayPlanna software finds the least cost orderin which to visit each location such that every location is visited once and the salesman ends up back at his starting location. The order in which to visit a given set of locations can be computed from a list of locations which are entered manully such as postcodes or Easting and Northing co-ordinates in the National Grid of Great Britain. More commonly, the locations are specified by a postcode in Great Britain which is read from a Microsoft Excel spreadsheet or an ASCII Text comma separated value (CSV) file exported from a business database which stores the names and addresses of customers, suppliers, employees and other contacts. The least-cost order can readily be computed and exported to a Microsoft Excel file or an ASCII Text CSV file.